Abstract: The answers to the three questions in The True Nature of All Things and to the four questions in The Philosopher -King all reveal Chuang Tzu’s skeptical tendency. Chuang Tzu’s skepticism does not appear from nothing but has a brewing process; it mainly develops from the“unknowing”theory of Lao Tzu，which gives the basic vocabulary，content，and paradigm and has already a preference of skepticism. Carrying forward the“unknowing”theory of Lao Tzu，Chuang Tzu develops this skeptical consciousness to its extreme，namely，the skepticism，and offers a home for his skepticism from“unknowing”to“genuine knowledge”. However，from then on，Chuang Tzu’s theory has found few to pass on，mainly because of its own defects.

Key words: Chuang Tzu, skepticism, Lao Tzu, unknowing, genuine knowledge